Deep brain simulation (DBS) comprises electrically stimulating with low-current pulses portions of the human brain controlling the movements, and more particularly the thalamus, the Luys nucleus, and/or the globus pallidus, which enables the patient to better control his/her movements. Such a stimulation is successfully used to treat Parkinson's disease, tremor, OCDs or dystoniae.
In practice, referring to FIG. 1, two sets of electrodes 10 are implanted in the brain for the electric stimulation thereof, each of these sets being arranged at the end of a flexible longilineal body made of a biocompatible material, also called “DBS” probes. The implantation of a probe comprises forming an opening in the patient's skull cap to introduce the probe through the trepanation to place its distal end at the desired location, using for this purpose real time brain imaging (scanner, MRI . . . ) and three-dimensional brain reconstruction. Due to the material forming it and/or to its diameter, the probe is usually highly flexible and difficult to introduce into the brain by simple pushing. Thereby, the probe is provided with a central channel into which the practitioner introduces a rod of low flexibility, called “stiffener”, which helps, or even simply makes possible, the progress of the probe into the brain by pushing.
During this operation, the patient is under local anesthesia so that tests can be performed as to the efficiency of the simulation. Once the probes are in place, the patient is then put under general anesthesia, and an extension 12 of each probe is arranged under the scalp and the neck skin for the connection of the probes to an electric cell stimulator 14 arranged under the patient's skin in subclavicular position.
In the following, term “distal” relates to a portion or an end of an element, intended to be in contact with the area to be treated. Term “proximal” relates to a portion or an end of the element, opposite to the distal portion or end and usually intended for the connection of the element to a stimulator.
Many DBS probes have thus been designed, for example, by Medscape©, Medtronics©, BostonScientic©, etc. . . . .
Referring to FIGS. 2 to 4, a DBS probe 16 usually comprises:
a flexible electrically-insulating cylindrical longilineal probe body 18, of small diameter, typically 1.3 mm, where the probe body may be a simple tube (MEDTRONIC) or a multi-lumen tube (Boston Scientific);
an assembly 20 of electric stimulation electrodes 20a, 20b, 20c, 20d arranged in a distal portion of body 18, and
an assembly 22 of power supply contacts 22a, 22b, 22c, 22d arranged in a proximal portion of body 18.
Electrodes 20a, 20b, 20c, 20d, often four, take the shape of electrically-conductive cylinders surrounding an outer surface of probe body 18. The latter further comprises at its center a hollow tube 26, void of material, which extends all along the length of body 18, and having a diameter usually from 0.45 to 0.55 mm to allow the introduction during the surgery of a metallic stiffener having a diameter from 0.3 to 0.35 mm.
An assembly 28 of electrically-insulated conductive wires 28a, 28b, 28c, 28d is wound around tube 26, respectively welded to electrodes 20a, 20b, 20c, 20d and to contacts 22a, 22b, 22c, 22d, and embedded in the material of probe body 18. Wires 28a, 28b, 28c, 28d typically have a diameter in the range from 100 μm to 150 μm.
The distal end of probe body 18 is further closed by a hemispherical plug 30 inserted into hollow tube 26. Thus, the central channel is tightly closed (except at the proximal end of the probe), to avoid any introduction of fluid into it, but also to avoid a contamination of the brain via the central channel during the implantation of the probe. Contacts 22a, 22b, 22c, 22d are generally also cylinders enclosing an outer proximal surface of probe body 18, and respectively connected to conductive wires 28a, 28b, 28c, 28d, with a dimension and spacing which may however be different from those of electrodes 20a, 20b, 20c, 20d. 
Referring to FIGS. 5 and 6, the electric connection of a DBS probe 16 comprises introducing the proximal portion thereof, provided with contacts 22a, 22b, 22c, 22d, into the channel of an electrical housing 32, comprising inner contacts/terminals which respectively come into contact with contacts of the probe 22a, 22b, 22c, 22d. Housing 32, which forms a simple electrical contacting area and thus comprises no electric control element, extends in an extension lead 34, provided with contacts 36 in a proximal portion for a connection to connectors 38 of an electric stimulator 40.
In parallel with deep electrical brain stimulation, deep optical brain stimulation arouses an increasing interest, particularly optical stimulation by means of a radiation in visible red or near infrared, for the treatment of the same diseases as those treated by the electric stimulation, as for example described in article “Red and NIR light dosimetry in the human deep brain” of A Pitzschke et al., Phys. Med. Biol. 60 2921, 2015. This new approach particularly induces the development of new probes provided, in distal position, with optical outlets, generally based on specific polymer materials which should have both the desired optical emission and biocompatibility properties.
The electrical stimulation only compensates for the lack of dopamine by exciting the Luys nucleus, but has no therapeutic effect on Parkinson's disease, which keeps on evolving. The results observed on preclinical tests show that an optical stimulation provides a cellular protection of the cells of the SNc, which cause Parkinson's disease as they degenerate. The combination of the two stimulation modes would provide a cellular protection and thus stop the disease, while decreasing the symptoms (akinesia, stiffness, tremor . . . ) by stimulating the Luys nucleus in patients already in an advanced phase of the disease. It is thus not excluded to combine the two approaches to stimulate a same area of the brain to treat a specific disease, for example, Parkinson's disease. This however implies multiplying the number of probes implanted in the brain, which is hardly conceivable. As a variation, it is possible to design probes which each comprise two sets of electrodes in distal position, one set of electrodes for electric stimulation and one set of electrodes for optical stimulation. This however implies a rather large optoelectrical emission area of the probe, and thus possible a treatment which has too low a spatial selectivity, in addition to the multiplication of the conductive wires to be provided in the probe. It is also possible to attempt designing electrodes which are adapted to both stimulation types, electrical and optical, and which are further biocompatible. The difficulty implied by the development of such electrodes can thus easily be conceived.